BS 6F 34:1984 download.Specification for Light and medium duty linen ( flax ) sewing thread for aerospace purposes.
1 Scope
BS 6F 34 specifies the requirements for light and medium duty linen sewing thread for aerospace purposes.
NOTE 1 The titles of the publications referred to in this standard are listed on the inside back cover. NOTE 2 The latest revision of an Aerospace Series standard is indicated by a prefix number.
2 General requirements
2.1 In addition to the requirements specified in clause 3 to 6 of BS 6F 34, the following sections and clauses of the latest edition of BS F 100 shall apply.
2.2 Threads manufactured in accordance with this standard shall comply with 2.2.1 and 2.2.2.
2.2.1 Freedom from defects
2.2.1.1 Threads shall have uniformity of thickness. construction, and component ply tension so that there are no visually irregular twist defects.
2.2.1.2 Threads of length per unit mass less than 6 000 rn/kg shall contain no thread knots.
2.2.1.3 Threads of length per unit mass greater than 6 000 rn/kg shall not contain more than two thread knots per package.
2.2.2 Length per unit mass. The length per unit mass of thread shall be determined in accordance with method A of BS 2010.
3 Yarn
3.1 The thread shall be manufactured from flax fibre (Linunz usitatissimum) in a three-fold construction.
3.2 The mass of the yarn shall have been reduced by not less than 10 %, by boiling.
NOTE The degree of boiling of the yarn should be determined from the manufacturer’s records, if available. Otherwise, the Residual Alkali Solubility of the thread should be determined and should not exceed 10 %.
4 Finish
4.1 Condition of material
The thread shall he supplied in one of the following conditions:
a) undyed and rotproofed:
b) undyed, rotproofed and wax finished;
c) dyed and rotproofed, or;
d) dyed, rotproofed and wax finished.
4.2 Dyeing
Where dyeing is required, the colour shall be specified by reference to an official standard,
e.g. BS 381C, or otherwise by pattern.
NOTE Reference to an official standard, e.g. BS 381C is preferable.
4.3 Rotproofing
The thread shall be treated with pentachiorophenyl laurate (PCPL) from aqueous emulsion in accordance with BS 2087-1, normal process,
4.4 Wax finishing
Where wax finishing is required, beeswax substitute microcrystalline hydrocarbon wax shall be used and the added mass due to the wax shall be 20 ± 5 %. Prior to waxing, the thread shall have been rotproofed in accordance with 4.3.
4.5 Surface finish
The thread supplied in accordance with 4.1 a) and 4.1 c) shall be polished, but substances which promote microbiological growth (e.g. starch or modified starch) shall not be applied.
5 Construction and properties of sewing threads
5.1 The thread shall comply with the requirements
given in Table 1.
5.2 The direction of final twist shall be Z.
6 Identification
The thread shall be identified for ordering purposes by the number of BS 6F 34,
i.e. BS 6F 54 together with the relevant designation number given in Table 1, the finish and, where required, the colour.
NOTE This identification may be codified. For example. thread no. 12 required dyed black and rotproofed may be identified as 138 6F 34(No. 12/black/PCPLIwaxed”.